Once you've worked as a writer and editor in the world of social media for a decade, the way I have, you start to notice patterns. For example, there are some stories that will never go viral, even if they are brilliant in every measurable way. That's because they lie in the "valley of ambiguity," which is sort of like the uncanny valley for viral journalism.

If a story is circulating in social media, even if it's a fancy character study for the New Yorker or incisive cultural analysis for the Atlantic, it's always chasing the viral tornado. Before the 21st century, stories became popular because people talked about them in other publications, or shared magazine and newspaper clippings with friends. Today, stories become influential if people share them on social media like Facebook, Reddit, Pinterest, and Twitter. In most cases, nobody is going to read a story if nobody shares it.

This leaves a lot of writers and readers wondering why the hell some stories go everywhere and some never make it past three likes on Facebook. Here is one theory, based on my own anecdotal experiences and those of many other people I've talked to in the industry. It's not a scientific theory, and you'll notice that the diagram I have used to illustrate it is something that began on the back of a napkin. Still, I think it can help us make sense of the way that virality has changed journalism in the 21st century.

Basically, there are two kinds of stories that tend to go viral. On one side of the diagram, you can see the most obvious genre of viral story: the meme, or the single, simple unit of information that we share because it's funny or makes us feel good. The purest version of the meme online is the LOLcat, usually just a picture with a caption, which is the perfect pick-me-up bit of portable content. What the LOLcat shares with self-help guides and human interest stories is an invitation to credulous enjoyment.

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TED videos, often seasoned with cheery platitudes, become viral for the same reason that grumpy cat pictures do. They don't ask us to think critically — just to enjoy, or be amused and enlightened without the time-consuming labor of skepticism and doubt clouding our clicks. Why do we want to share these stories? Because in some sense they are not open to interpretation. You don't have to worry whether your friends will wonder why you shared this – it's obvious.

The same goes for viral journalism on the other side of my chart. These stories, like explainers, how-to guides, Mythbusters-style debunkery, and truth-telling investigative journalism, are in some ways the opposite of a stupid video or a LOLcat. They are about truth, rather than amusement. But in fact, they go viral for exactly the same reason LOLcats do. They are not open to interpretation.

In fact, the main goal of a lot of these stories is to clear up confusion the way Nate Silver did during the election in his analysis of polling. A how-to story is all about leading you through a process without getting you lost. A hard-hitting investigative report that uncovers a nugget of genuine truth is the ultimate viral hit. It's a story that promises we can at last know exactly what has happened, or how to feel about something. We want to share these stories because they appeal to our urge to have the definitive explanation of what is true and right.

To share a story is in part to take ownership of it, especially because you are often able to comment on a story that you are sharing on social media. If you can share a piece of information that's an absolute truth – whether that's how to uninstall apps on your phone, or what the NSA is really doing – you too become a truth teller. And that feels good. Just as good as it does to be the person who has the cutest cat picture on the Internet.

So that leaves us with the stories that don't make it. These are the articles and essays that have fallen into the valley of ambiguity – reports on important scientific findings with difficult-to-interpret results, political news with a long and tangled back story attached, and opinion essays that require us to account for points of view that may be unfamiliar or strange. There is no satisfaction in knowing that the Higgs boson has sort of been found, but sort of not. And nobody wants to risk alienating friends with a piece of opinion writing that might or might not be offensive – you're not even sure.

Who wants to share a story that can be misunderstood? Nobody wants to take ownership of a political article where there is no truth – only further information, and complex developments that even experts can't agree on.

It's not that we don't want to be the bearers of bad news. In fact, plenty of stories that go viral are nasty, negative and mean. We just want to share stories that make us seem like we know something.

Most of all, we don't want to say something that we didn't intend. And that is the danger with any story that falls into the valley of ambiguity. We can't be sure how people will take it. We don't want to risk our reputations on a story that can be taken more than one way.

More than anything, the fear of a smeared reputation is what creates that dip in virality. Sharing a story means that in some sense we stake our reputation on it. That's why sharing a story is not the same thing as enjoying a story, reading a story, or even learning from a story.

I know for certain that there are plenty of stories that get read, but not shared. I have seen the statistics on io9's back end. But when we measure a story's success by virality, which is what we must do in the age of social media, the content of our popular culture changes. We measure success by what people aren't afraid to share with their neighbors, rather than what people will read on their own.